Bizarre Birds - The South American Hoatzin

One of a Kind - A Monotypic Species

National Bird of Guyana - The Hoatzin

The hoatzin bird is a monotypic species, being the only representative of its genus Opisthocomus. There are a great number of monotypic species, some of which are the numbat, pronghorn, okapi and moose. Guyana has chosen the hoatzin and the jaguar as its national bird and animal symbols.

It is often considered one of the most primitive off all birds and has a quirky charm with its bizarre shape, striking colours, Mohican haircut and dramatic cape-like wings. Two claws on the wing digits of the chicks are evidence to some scientists of reptilian ties.

The genus name is an Ancient Greek word meaning 'wearing long hair behind' and refers to the large crest. Its full taxonomic name is Opisthocomus (meaning 'pheasant') hoazin but there is much debate about its true position in the taxonomy system.

The hoatzin has the common name of 'stinkbird' as it has a pungent odour that can make your eyes water. The stench comes from its unique (for a bird) digestive system and is said to be akin to cow manure. Other common names are reptile bird (because of the odour and harsh, monotonous call) and flying cow because of its diet and clumsy flying manner. It has been grouped with a number of different bird types but doesn't really fit with any. They have been aligned variously with rails, cranes, tinamous, doves and even cuckoos but they remain unique and odd.

RangeThe hoatzin is found in the Amazon and Orinoco delta region of South America.

HabitatThe preferred habitat of the hoatzin includes swamplands, marshy areas, mangroves and riverine forest areas. They are found in old backwater lagoons and cut-off river channels but avoid swift-moving water. They are not good fliers and even short flights across channels are accompanied by lots of noisy protestations.

DescriptionThe hoatzin is the size of a pheasant with a length of 65 cm, a long neck and small head. It weighs about 816 grams. It has a spiky, rufous crest and maroon or red eyes in a naked blue face. The tip of the long sooty-brown tail is buff. The upperparts are dark with buff edging on the wing coverts and streaks on the mantle and nape. The underparts are buff. Hidden underparts are a rich chestnut but not seen until the bird spreads its wings. The females are slightly smaller with lower crests. Three toes face forward and one backwards. The wings form a dramatic cape about the bird and the extravagant tail is fanned out to aid the bird's balance as it clambers about the vegetation.

They are awkward birds, clumsy in flight, often crash-landing and with a flouncing gait. There is a leathery bump on the bottom of the crop which helps the bird balance as it clambers among the branches.

BehaviourThe hoatzin is relatively tame and can be approached although frequent interaction causes it stress. It forms groups of up to 40 birds and occupies densely packed territories which may include 20 odd nests in one tree. The hoatzin has a number of vocalisations which the bird employs to keep contact with others in the group and to warn off intruders. They often vocalise in unison with a medley of hoarse cries, hisses, growls and grunts. Chicks also vocalise when begging for food.

Hoatzins forage early morning and late afternoon for periods of about thirty minutes. The rest of the day is spent resting and digesting their meal.

NutritionThe hoatzins are folivores and ingest mainly leaves plus a few flowers and fruits. Over 50 species of leaves are consumed. Its diet appears to be 82% leaves, 10% flowers and 8% fruit.

It has an unusual digestive system and is the only bird known to have a foregut fermentation process. This process is more similar to a cow or sheep than to a bird. But, while ruminants have a rumen where bacterial fermentation takes place, the bird has a crop. The crop is really an enlargement of the oesophagus. Because the crop is so large, it displaces the flight muscles and keel of the sternum making the hoatzin a very clumsy flier. The unpleasant odour comes from the aromatic compounds in the leaves and the bacterial fermentation. The manure-like odour ensures that the bird is not hunted for food unless times are very, very tough.

Because its diet of leaves is so low in nutrients (cf koala and panda bear), it needs to eat a huge amount. The oesophagus and enlarged crop serve as fermentation chambers. Inside these chambers, anaerobic bacteria secrete enzymes which serve to break down the largely indigestible cellulose of the plant tissue.

Leaves are chewed before being swallowed, and ridges in the crop aid in breaking down the leaf bulk further. Nestlings are fed this regurgitated material.

ReproductionThe hoatzin is a seasonal breeder and breeds during the rainy season. They nest in small colonies, constructing a stick nest in trees which overhang water in seasonally flooded forests.

Four or five eggs are laid in a clutch. These have blue or brown spots. Incubation is about a month and the young chicks can start to feed themselves 10 to 14 days later.

When the chick is first hatched, it has claws on the thumb and first finger, and over-sized feet. These enable it to climb with great dexterity until the wings are strong enough to support it when flying. The claws disappear as the bird matures.

ThreatsThe Great Black Hawk preys on hoatzin nesting colonies and adults will attempt to divert the hawk while the chicks move into the thickets and hide. If discovered, they drop into the water and swim underwater to get away, later using their clawed wings to get back to their nest. Adult birds are unable to swim.

Its preferred habitats are disappearing in some areas but not as quickly as terra firme forest. The bird is reasonably common in a large part of its range. Because of its foul smell which seems to permeate the flesh, it is rarely hunted although the eggs may be collected for food.

ConservationThe hoatzin is the national bird of Guyana. It is listed by the IUCN as 'of least concern'.

Comments

JudyE
They have a really rakish look, don't they? The chick looks positively prehistoric! Thanks for the comment.

Feb 16, 2012 2:46am

vicdillinger
It is interesting you mentioned prehistoric, because this living specimen very nearly matches an artist's conception of a member of the dinosaur age, a feathered dinosaur that the shot you have in profile in flight looks almost like his idea. Amazing -- the feathered saurs were posited just a few years ago as the true ancestors of modern birds and you've got one here that could be a close cousin. Good read -- not so sure I’d like to be around something so smelly, but the plumage is gorgeous.

Feb 18, 2012 11:15pm

healthy1chef
Beautiful bird and interesting facts about the Hoatzin, nature is pretty smart to make this bird a stinky one to keep it safe from predators. Cheers!